shmtool.c

操作系统Interprocess Communication（IPC）实验源码。 在Unix的内核环境中

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#define SEGSIZE 100

void writeshm(int shmid,char *segptr,char *text);
void readshm(int shmid,char *segptr);
void removeshm(int shmid);
void changemode(int shmid,char *mode);
void usage();

int main(int argc,char *argv[])
{
  key_t key;
  int shmid,cntr;
  char *segptr;

  if (argc==1)
    usage();

  key=ftok(".",'S');
  if ((shmid=shmget(key,SEGSIZE,IPC_CREAT|IPC_EXCL|0666))==-1) {
    printf("Shared memory segment exisits-opening as client\n");
    if ((shmid=shmget(key,SEGSIZE,0))==-1) {
      perror("shmget");
      exit(1);
    }
  } else {
    printf("Creating new shared memory segment\n");
  }

  if ((segptr=shmat(shmid,0,0))==-1) {
    perror("shmat");
    exit(1);
  }

  switch (tolower(argv[1][0])) {
  case 'w':
    writeshm(shmid,segptr,argv[2]);
    break;
  case 'r':
    readshm(shmid,segptr);
    break;
  case 'd':
    removeshm(shmid);
    break;
  case 'm':
    changemode(shmid,argv[2]);
    break;
  default:
    usage();
  }
  return 0;
}

void writeshm(int shmid,char *segptr,char *text)
{
  strcpy(segptr,text);
  printf("Done...\n");
}

void readshm(int shmid,char *segptr)
{
  printf("segptr:%s\n",segptr);
}

void removeshm(int shmid)
{
  shmctl(shmid,IPC_RMID,0);
  printf("Shared memory segment marked for deletion\n");
}

void changemode(int shmid,char *mode)
{
  struct shmid_ds myshm_ds;

  shmctl(shmid,IPC_STAT,&myshm_ds);
  printf("Old permissions were:%o\n",myshm_ds.shm_perm.mode);
  sscanf(mode,"%o",&myshm_ds.shm_perm.mode);
  shmctl(shmid,IPC_SET,&myshm_ds);
  printf("New permissions are:%o\n",myshm_ds.shm_perm.mode);
}

void usage()
{
  fprintf(stderr,"shmtool-A utility for tinkering with shared memory\n");
  fprintf(stderr,"\nUsage:shmtool (w)rite <text>\n");
  fprintf(stderr,"                (r)ead\n");
  fprintf(stderr,"                (d)elete\n");
  fprintf(stderr,"                (m)ode <octal mode>\n");
}